Icon LinkSignature Verification

fn verify_signature(i: u64) -> u64 {
    // Discard any out of bounds signatures
    if (i >= tx_witnesses_count()) {
        return 0;
    }
 
    let tx_hash = tx_id();
 
    let mut j = 0;
 
    while j < 3 {
        let current_signature = tx_witness_data::<B512>(j);
        
        let current_address = ec_recover_address(current_signature, tx_hash).unwrap();
 
        if current_address.value == SIGNERS[i].value {
            return 1;
        }
 
        j += 1;
    }
    return 0;
}

1. Parameter i: This parameter represents the index of a signer in a predefined list of signers defined in the configurable. It's used to identify which signer's signature the function is currently attempting to verify.
2. Signature Verification Loop: The function then enters a loop, iterating up to three times. This loop represents an attempt to verify the signature against up to three pieces of witness data (signatures) attached to the transaction.
   • Signature Recovery: Inside the loop, for each iteration defined by j, it retrieves the current signature (current_signature) from the transaction's witness data using tx_witness_data::<B512>(j). It then attempts to recover the address that generated this signature (current_address) by using the ec_recover_address function, which takes the current signature and the transaction hash as inputs.
   • Address Matching: After recovering the address, the function checks if this address matches the address of the ith signer in the SIGNERS list. If a match is found, it means the signature from one of the signers has been successfully verified, and the function returns 1.

while j < 3 {
    let current_signature = tx_witness_data::<B512>(j);
    
    let current_address = ec_recover_address(current_signature, tx_hash).unwrap();
 
    if current_address.value == SIGNERS[i].value {
        return 1;
    }
 
    j += 1;
}
return 0;

3. Return Value: The function returns 1 if a matching signature is found for the ith signer, indicating successful verification. If no matching signature is found after checking up to three signatures, the function returns 0, indicating that the signature for the ith signer could not be verified.